1. Field of the Invention
The present invention relates to a tube joint which makes it possible to connect, for example, a tube member such as a tube to a fluid pressure apparatus in a liquid-tight manner or in an air-tight manner.
2. Description of the Related Art
A tube joint concerning a conventional technique (see, for example, Japanese Utility Model Publication No. 7-20471) is shown in FIG. 8.
The tube joint 1 comprises an inner ring 3 for being pressed and inserted into one end of a tube member 2 so that the inner ring 3 protrudes from the one end of the tube member 2 to increase the diameter of the tube member 2 at the one end, and a main joint body 5 having a socket 4 formed at one end thereof for inserting a plug portion of the tube member 2 into which the inner ring 3 has been pressed and inserted. An external thread 6 is threaded over an outer circumference portion of the main joint body 5. A press ring 8 is externally fitted to the one end of the main joint body 5 through an internal thread 7 which engages with the external thread 6.
In this case, a seal section 9 is provided at a deep portion of the socket 4. The seal section 9 is formed to cross an axis of the socket 4 so that a seal section disposed at an inner end of the inner ring 3 protruding from the one end of the tube member 2 is allowed to abut against the deep portion of the socket 4. The sealing performance is secured by the aid of the seal section 9.
However, in the case of the tube joint 1 concerning the conventional technique, for example, when a pressurized fluid having different viscosity is used, it is necessary that the tube member 2, which has been once connected to the tube joint 1, should be exchanged for another tube member (not shown) having a different caliber. As a result, it is necessary to prepare a plurality of tube joints applicable to calibers of various tube members, resulting in an inconvenience that the equipment investment is expensive.
Further, in the case of the tube joint 1 concerning the conventional technique, when the tube member 2 is exchanged for another tube joint (not shown) having a different caliber, it is necessary that the entire tube joint 1 should be exchange. Therefore, it is required to perform the operation to remove the tube joint 1 connected to the fluid pressure apparatus, and perform the operation to attach the tube joint 1 thereto, in which the operation process is complicated.
Moreover, it is necessary to manage a plurality of tube joints corresponding to the calibers of the tube members 2, resulting in an inconvenience that the management cost is expensive.
Furthermore, the seal section 9 of the tube joint 1 concerning the conventional technique involves the following inconvenience. That is, the seal is effected in a state in which the seal section disposed at the inner end of the inner ring 3 makes surface-to-surface contact with the deep portion of the socket 4. Therefore, the force (pressure) for pressing the seal surface, i.e., the surface pressure exerted on the seal surface tends to be lowered, resulting in decrease in sealing performance.